"... Though Jonah refers to the creature as a דָּג (fish) four times (1:17 [2x], 2:1, 2:10), the ancients were acutely aware of the term’s ambiguity ... In Jonah, the ambiguity of the דָּג, coupled with its enormous size, naturally encouraged the ancients to identify it as a type of giant sea monster known as a תַּנִּין “Tannîn.” Thus, the authors of the LXX rendered הַתַּנִּינִ֖ם הַגְּדֹלִ֑ים “the great sea monsters” in Genesis 1:21 similarly: τὰ κήτη τὰ μεγάλα. The term תַּנִּין refers generally to a type of serpentine creature of which Leviathan is one kind. Thus, the word תַּנִּין takes the definite article (Genesis 1:21, Isaiah 27:1, Jeremiah 14:6, 51:34, Ezekiel 29:3, Nehemiah 2:13), whereas לִוְיָתָן never does. Nevertheless, traditions concerning Leviathan are not entirely consistent. Thus, some texts understand the creature as possessing multiple heads, others see it as having one. Sometimes it also is equated with a lion or a sea monster with lionlike features ..."